| With the continuous development of urban transportation, underground transport system is being gradually improved. Underpass as the most common underground traffic structure, frequently distributed at various city roads. In this paper, a city underpass project on soft ground, its ground handling and channel structure selection were analyzed and compared. In the end, We consider various factors and finally select cement mixing pile and high pressure spraying pile of two foundation treatment methods, choose frame culvert and cover culvert two forms of channel structures.The paper use the software MIDAS GTS to analysis the whole model which contains both the structure and the pile foundation. For the purpose of the best foundation treatment of each structure, pile spacing, pile length and the form of the piles arranged in the cross section are considered respectively. Then calculate the structure with the load structure method in some load combinations. The results are referred to arrange the steel reinforcement of the culverts. Finally, the economy of the two schemes were compared, summed up the advantages and disadvantages of the two programs and make a few suggestions.The results show that for the frame culvert, the foundation treatment effect are essentially the same by comparing the high pressure spraying pile foundation and the cement mixing pile foundation. While the number of the high pressure spraying pile is half way less than the cement mixing pile; the square layout of the piles is better than the triangle layout; as the pile length increases, the settlement of construction is reduced. When the pile length reaches 10 m, the settlement gradually reduced to flatten and thus launched the present structure of the cement mixing pile effective length should be 10 m nearby. According to the experience of actual projects, cement mixing pile should better pass through the soil soil and enter the soil whose strength is better. So the pile length finally determined as 12 m.For the cover box culvert structure, due to its heavy weight, high strength requirements of the foundation, it needs more piles with the cement mixing pile foundation than with the high pressure spraying pile foundation. And the depth of the ground treatment requires 20 m which the cement mixing pile can not carry out. So the cover culvert choose the high pressure praying pile foundation treatment; We find that the triangle layout of the piles is better than the square layout at the same pile spacing and number.Through cost comparison of two structural engineering solutions, frame culvert with cement mixing pile foundation treatment economy as a whole is better than the cover culvert with high pressure spraying pile foundation treatment. So to the background of this project, the rational economic program should be frame box culvert with cement mixing piles. |
